Origin of Life- Focussing Chemical Evolution
This article is focused particles on chemical evolution. Earth developed around 4.6 billion years back by condensation of elm or cloud of cosmic dust and gases. Not body knows what actually happened. Well its beyond our reach to go into past and observe the events one by one. But we made an estimate and statistics based on the evidences(fossils) and process taking place on the earth. Many experiments were done. And finally it was concluded that the origin of life took place from chemical evolution followed by biological evolution.
What actually happened?
At first, there were only gases and dust particles. It was made up of radioactive elements. They soon started decaying and formed heat. It was followed by condensation and cooling resulting in stratification with heavier elements (e.g. Nickel, Iron). At this time, the surface was as hot as melted iron. Due to this the lighter elements like Hydrogen, Carbon, Oxygen were present in atomic state. But soon the formation of molecules started taking place. As the time passed, the temperature came down and its surface cooled down. The lighter elements interacted with each other and formed water, methane, ammonia, Carbon monoxide, carbon dioxide and hydrogen cyanide.
On the similar way, nitrites and oxides also formed. Atmosphere of this period is called reducing atmosphere. However, there was no ozone layer. Therefore, the UV rays were highly active on the surface. With the time our earth became solidified enough to have large depressions and elevations all around. Since the temperature was high, the water was mainly present in the form of steam. The rate of evaporation was fast. Average temperature was around 50-60 Celsius. Lightening was frequent. The intense heat of volcano and radioactive decay of various elements contributed a large amount of energy merging methane, ammonia and other molecules with each other and formed new complex molecules. This resulted in the formation of simple organic molecules. These were mainly alcohols, Aldehydes, amino aids, sugar etc. An experimental proof of same has also been given. The proof was given by the famous scientist Stanley L. Miller on the theory that life originated from preexisting non-living matter. This helped the basic theory to be widely accepted by the people.
Soon larger molecules were formed. The simple organic molecules remained in low concentration due to development of steady state or equilibrium. Polymerization required their concentration, a source of energy and evaporation of water. this occurred on the shores of water bodies where clay and other minerals helped in their aggregation and formation of a short of sludge. he molecules came in contact with each other and reacted simultaneously. They formed newer molecules. The environment was oxygen free. Radiations, lightening volcanic eruptions were frequent. All these along with solar energy provided the energy undergo more chemical reactions. Simple sugar condensed to form pep-tides, polypeptides and even proteins. On the similar way polynucleotides condensed to form nucleic acid.
The basic elements were formed.It paved the entry of processes involving various biological activities on after another.All these reactions occurred without any enzyme, DNA, RNA or ribosome. In this way, the basic condition for origin of life was fulfilled. But it was just the beginning of a source of life on earth. This nearly took billions of year(don't know the exact figure). It was followed by the biological evolution in which the first of life developed. It will be discussed separately in another article.
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